Method of preventing vapor lock during engine operation and of fuel leakage to carburetor after engine stoppage

ABSTRACT

Vapor lock which might otherwise occur in its fuel supply pump during high temperature operation of a liquid-fuel engine, is minimized or eliminated by continuously withdrawing a small fraction of the flow liquid from the bottom level of the pump outlet conduit and reintroducing it at the top level of the pump inlet conduit. Also, after pump and engine stoppage, pressurized liquid remaining in the pump to carburetor (outlet) conduit, is prevented from dribbling into the carburetor and vaporizing into adjacent space (and creating a fire hazard and air pollution) by relieving the back-pressure in such conduit and then closing same without breaking the liquid column, by valve means in the (sigmoid) pump bypass. Such small capacity bypass may be left open during pump and engine function, without interfering with normal operation, and closes in response to decreased backpressure in the line when the pump stops.

United States Patent Norton 1 July 4, 1972 54] METHOD OF PREVENTINGVAPOR 2,964,029 12 1960 TlllOni ..123/139 LOCK DURING ENGINE OPERATION3,199,458 8/1965 11661111 ..417/311 AND OF FUEL LEAKAGE TO CARBURETORAFTER ENGINE STOPPAGE Neil C. Norton, P. O. Box 104, Gardena, Calif.90247 Filed: June 26, 1970 Appl. No.: $0,074

Related US. Application Data Continuation-in-part of Ser. No. 726,308,May 3, 1968, Pat. No. 3,559,680, which is a continuation-inpart of Ser.No. 616,594, Feb. 16, 1967, abandoned.

Inventor:

References Cited UNITED STATES PATENTS 1/1932 Miller ..261/72 PrimaryExaminer-William R. Cline Attarneyl-loward L. Johnson [5 7] ABSTRACTVapor lock which might otherwise occur in its fuel supply pump duringhigh temperature operation of a liquid-fuel engine, is minimized oreliminated by continuously withdrawing a small fraction of the flowliquid from the bottom level of the pump outlet conduit andreintroducing it at the top level of the pump inlet conduit. Also, afterpump and engine stoppage, pressurized liquid remaining in the pump tocarburetor (outlet) conduit, is prevented from dribbling into thecarburetor and vaporizing into adjacent space (and creating a firehazard and air pollution) by relieving the back-pressure in such conduitand then closing same without breaking the liquid column, by valve meansin the (sigmoid) pump bypass. Such small capacity bypass may be leftopen during pump and engine function, without interfering with normaloperation, and closes in response to decreased back-pressure in the linewhen the pump stops.

5 Claims, 2 Drawing Figures METHOD OF PREVENTING VAPOR LOCK DURINGENGINE OPERATION AND OF FUEL LEAKAGE TO CARBURETOR AFTER ENGINE STOPPAGEThis is a continuation-in-part of Ser. No. 726,308, filed May 3, 1968,now US. Pat. No. 3,559,680, which is a continuationin-part of Ser. No.616,594, filed Feb. 16, 1967, now abandoned.

BACKGROUND OF THE INVENTION Motorists driving in elevated temperatures,such as the summer-time desert, as well as in rarefied atmospheres suchas high mountain areas, have become familiar with the problem of vaporlock. This is caused by volatilization of liquid fuel in the pump and inits delivery line to the carburetor. Partial vaporization cuts down thequantity of liquid fuel being pumped to the carburetor, in part becauseof a gas pocket being retained in the pump or outlet, so that the gasreduces the area left for liquid passage. The engine chokes or sputters.At this point, the motorist may stop the car and throw water on the fuelpump in an effort to condense the trapped vapor, or to try to get thepump to purge it from the system. However if such effort is unsuccessful(or is not resorted to), further volatilization of the fuel maysubstantially completely fill the pump with vapor so that no liquid fuelatall is passed to the carburetor and the pump is locked; obviously themotor then stalls and the vehicle stops. When the vaporization hasproceeded to this extent, it may not be reversible simply by cooling thepump since the liquid flow or column has been broken. The pump has to beprimed with liquid in order to restore its function.

Aside from cooling the engine, this problem has been dealt with byproviding gasoline blends or the like, having a higher boiling point;such blends are then less effective at lower temperatures. Obviously asimpler solution of the problem would be desirable.

Still another irritating problem of long standing has been thatresulting from the column of pressurized fuel remaining in thepump-to-carburetor conduit when the pump and engine are stopped.Especially in the presence of a leaky needle valve in the carburetor,this liquid dribbles into the carburetor and evaporates into thesurrounding space. Especially in a closed space such as the enginecompartment of a small boat, this concentration of combustable gases ishighly explosive upon introduction of a spark, such as that provided byengine startup. Many fires which completely destroyed the marine craftor motor boat have had such origin. Such accumulated (gasoline) vapor isalso toxic to persons (or animals) having to inhale it. Beyond that, itis a general pollutant of the atmosphere, which when multiplied by thelarge number of wet carburetors on both land vehicles as well as marinecraft, dumps a tremendous tonnage of contaminants into the air over anyarea which contains an active concentration of internal combustionengines. In brief, such undesirable venting of unburned fuel vaporresults both from conditions associated with vapor lock and fromcarburetor needle valve leakage. Both conditions benefit from thepresent invention.

BRIEF SUMMARY OF THE INVENTION As noted in the preceding abstract,leakage from the pump to carburetor after engine shut-down is preventedby relieving the pressure of the trapped liquid-fuel in the pump outletconduit, while retaining the column of liquid unbroken in this line sothat it neither dribbles into the carburetor or drains back toward thefuel reservoir (as it would if the latter were at a lower level). Vaporlock of the fuel pump during operation, is prevented by bleeding of asmall line of liquid from the lower level of the pump outlet conduit andreturning it to the upper level of the pump inlet line. Such acirculation (bypass) is in continuous operation during operation of thepump, typically by use of an S-shaped or sigmoid bypass conduit of smallinternal cross section relative to the cross section of the pump inletand outlet conduits. Such bypass can additionally be used to relieve thepressure of the fuel trapped in the outlet conduit after engine and pumpshut-down, by provision in the bypass conduit of a normally-open valvewhich closes (after pump stoppage) in response to decrease ofback-pressure in the outlet line. Thus a single and simply-installedunit or assembly will perform both functions or method-steps insequence, and solely in response to movement of liquid-fuel through thepump outlet conduit.

In this connection it may not be completely understood why the method ofrelieving vapor lock depends upon withdrawing the bypass stream from thelower outlet level and reintroducing it to the upper (pump) inlet level.However, (vertical) bypass loops from top to top, as well as from bottomto bottom are singularly unsuccessful; so are bypass lines disposed atthe same horizontal level; so is an S-loop from top of outlet to bottomof inlet. It may be that withdrawal from the bottom outlet level permitsbubbles to be swept to the carburetor rather than into the bypass and bysuch fractionation relieves vapor which has started to form in the pumpand thus prevents its accumulation in situ. In any event, the twoproblems (vapor lock and wet carburetor) which were not previouslythought to be associated, are thus solved simultaneously or at least insequence by these two method steps.

The present method which both counteracts threatened or potential vaporlock during engine operation, and prevents leakage of liquid-fuel fromthe pump to the carburetor (and its subsequent vaporization into theatmosphere as from a flooded carburetor) after pump stoppage, may beeffected by use of a simple pump bypass assembly such as hereinillustrated, which unit can be readily installed on conventionalinternal combustion engines whether stationary engines or those used topropel land vehicles or marine craft (as well as airplanes).

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of mybypass assembly connected to an automotive fuel pump (shown in brokenlines), with the fuel reservoir and carburetor indicated schematically;and

FIG. 2 is an axial sectional view of the bypass valve unit alone, seenin upright, operative position.

DESCRIPTION OF A PREFERRED EMBODIMENT As here illustrated, aconventional liquid-fuel pump P is located intermediate the length ofthe fuel line L which extends from a fuel reservoir R (i.e., gasolinetank) to the carburetor C of an internal combustion engine (not shown)which utilizes the carburetor-atomized fuel in the usual manner. Theportion of the fuel line extending from the reservoir to the pump may bedesignated as the inlet conduit 10, and the portion from the pump to thecarburteor as the outlet conduit 12. It will be understood that anunbroken stream or column is maintained in the line, whether moving ornot. The liquid in the reservoir R is ordinarily under ambientatmospheric pressure, while the fuel in the outlet conduit 12 is underthe pressure added by the pump P, which is usually on the order of about1 to 10 p.s.i.g. with diaphragm-type pumps.

Essentially the present assembly consists of a pair of T- fittings 14,16, a (S-shaped) bypass conduit 18 and a valve assembly 20. One Tee, 16,is connected between the inlet conduit l0 and the inlet port 6 of pumpP, with its upstanding nipple 7 coupled to the valve assembly 20 aboveit. The other Tee, 14, is inserted between the outlet conduit 12 and theoutput port 8 of the pump P with its downtumed nipple 17 joined to thedownwardly concave segment 19 of the bypass conduit 18. The successiveconvex segment 21 of the bypass conduit is received in the aperturemount 9 of the upper housing piece 24 of the valve assembly 20.Preferably the internal diameter of bypass conduit 8 is about [/6 orless that of the outlet conduit 12.

The valve assembly proper 20 is formed of a longitudinally apertured,two-piece housing shell or tube 24, 26 threadedly coupled together atthe insertion neck 27 of the lower piece 26. A metering plug 28 isformed with an axial bore 11 which defines the flow capacity of thebypass 18, being threadedly mounted at in a tapped end-socket 12 of thelower housing 26. A slotted end 31 enables axial adjustment of the plug28, which at its inner end 23 forms a seat for the lower end of acompression spring which is loosely disposed within the housing chamber29. At the upper end of the housing 26, it is peripherally relieved at15 and axially drilled partway to fonn a restricted bore 33. At theinner end of the bore 33 an outstepped annular shoulder 32 forms'a seatfor a check ball 22, the underface of which is supported by the terminalcoil 34 of the spring 30. Below the stepped area, the channel tapersoutwardly at 36; into which tapered or conic section the valve 22partially projects even when seated, and into which it is progressivelythrust by increased back pressure from the passage 35. It will be seenthat the ball is in a position of gravitational descent, supported onlyby the weak spring 30, so that a comparatively small back pressure (e.g.Va p.s.i.g. or less) in the line 18-35-33 will serve to open it.However, when such minimum back pressure fails, it is immediately closedby the tension of spring 30 (which tension can be set or adjusted bypositioning the plug 28).

Thus it will be seen that the added assembly has a dual function: Whenthe pump P is operating, the return flow of liquid through the openbypass 18, which is actually metered to a small trickle by the smalldiameter of the passage 33, does not appreciably curtail the main fuelflow through the supply line L; but the bottom-level pickup provided bythe descendingly bowed segment 19 of the bypass has been found to beparticularly effective (from comparison with a top-side pickup from thesame outlet conduit location by an over-the-top-of-pump C-shapeconduit)to minimize or eliminate vapor lock in the operating pump. Secondly, thevalve 22 which is lightly loaded by the spring 29 so as to open at a lowback pressure in the bypass 18, although continually open during normalpump operation, is successively functional after cessation of pumpaction has stopped the main fluid flow through the supply line 12-10. Atsuch time, the still-open valve first equalizes the line pressure of thecarburetor side 12 against the unpressurized feed line 10, and thenautomatically closes so as to still retain liquid in the whole line(even in the event of a leaking carburetor needle valve). On the otherhand, if for any reason the pressure on the reservoir side of the pumpshould exceed that on the opposite side after the pump has stopped, thevalve 22 would close at once so as not to exert this additional pressureagainst the carburetor needle valve. It is notable that this overall orcomposite result is obtainable without any alteration of an existing orinstalled pump, and merely by incorporation because of the Tees 14, 16at connections already present on the fuel pump of the presentsimplified and highly effective, self-operating structure.

It will be clear to those skilled in the art that changes ofconstruction and operation may be made within the present inventiveconcept, and therefore this disclosure is not to be limited to theprecise details shown in the drawings and particularly described in thespecification by way of example, but it is my intention to claim theinvention broadly as hereafter defined.

What is claimed is:

1. In a method of moving a liquid-fuel supply from a liquidfuelreservoir by a pump inlet stream and pumping the fuel to a carburetor ofan engine by a pump outlet stream so as to move liquid fuel to thecarburetor from the reservoir at a normal operating pressure of thepump, the steps for restraining fuel entrance to the carburetor from thepump outlet stream after pump stoppage, comprising:

back-relieving substantially all pressure in the outlet stream byreverse movement of a small stream of the liquid fuel having a verysmall cross-sectional flow area in respect to an internal cross sectionof the outlet stream so as to bypass the pump after cessation of pumpoperation until the pressure in said outlet stream is substantiallyequalized with the pressure in said inlet stream, and then stopping saidreverse movement in response to decline of backpressure in said outletstream so as to retain unpressurized liquid which was in the outletstream from draining into the carburetor after the pump has stopped.

2. The method of the preceding claim 1 wherein continuously during pumpoperation said small stream is enabled to move to a top level of theinlet stream from a bottom level of the outlet stream, therebyminimizing occurrance of vapor lock in said pump.

3. In a method of moving a liquid-fuel supply from a liquidfuelreservoir by a pump inlet stream and pumping the fuel to a carburetor ofan engine by a pump outlet stream so as to move liquid fuel to thecarburetor from the reservoir at a normal operating pressure of thepump, the improved step comprising:

relieving potential or actual fuel vaporization in the pump or outletstream by continually passing a small stream of the liquid fuel from abottom level of the outlet stream to a top level of the inlet streamthereby reverse bypassing the pump and enabling purging of vapor formedtherein so as to maintain a continuous supply of liquid fuel to thecarburetor and prevent severance of such supply by occurrance of vaporlock in the pump.

4. The method of the preceding claim 3 wherein said small stream ofbypassing liquid fuel enters the pump inlet stream by a downwardlyconcave segment of a sigmoid path arising from the bottom level of theoutlet stream.

5. The method of the preceding claim 3 wherein upon pump stoppage, flowof said small stream of bypassing liquid fuel is stopped in response todecline of backpressure of the pump outlet stream, thereby preventingpump-pressurized liquid which was in the outlet stream from draininginto the carburetor after the pump has stopped.

1. In a method of moving a liquid-fuel supply from a liquid-fuelreservoir by a pump inlet stream and pumping the fuel to a carburetor ofan engine by a pump outlet stream so as to move liquid fuel to thecarburetor from the reservoir at a normal operating pressure of thepump, the steps for restraining fuel entrance to the carburetor from thepump outlet stream after pump stoppage, comprising: back-relievingsubstantially all pressure in the outlet stream by reverse movement of asmall stream of the liquid fuel having a very small cross-sectional flowarea in respect to an internal cross section of the outlet stream so asto bypass the pump after cessation of pump operation until the pressurein said outlet stream is substantially equalized with the pressure insaid inlet stream, and then stopping said reverse movement in responseto decline of backpressure in said outlet stream so as to retainunpressurized liquid which was in the outlet stream from draining intothe carburetor after the pump has stopped.
 2. The method of thepreceding claim 1 wherein continuously during pump operation said smallstream is enabled to move to a top level of the inlet stream from abottom level of the outlet stream, thereby minimizing occurrance ofvapor lock in said pump.
 3. In a method of moving a liquid-fuel supplyfrom a liquid-fuel reservoir by a pump inlet stream and pumping the fuelto a carburetor of an engine by a pump outlet stream so as to moveliquid fuel to the carburetor from the reservoir at a normal operatingpressure of the pump, the improved step comprising: relieving potentialor actual fuel vaporization in the pump or outlet stream by continuallypassing a small stream of the liquid fuel from a bottom level of theoutlet stream to a top level of the inlet stream thereby reversebypassing the pump and enabling purging of vapor formed therein so as tomaintain a continuous supply of liquid fuel to the carburetor andprevent severance of such supply by occurrance of vapor lock in thepump.
 4. The method of the preceding claim 3 wherein said small streamof bypassing liquid fuel enters the pump inlet stream by a downwardlyconcave segment of a sigmoid path arising from the bottom level of theoutlet stream.
 5. The method of the preceding claim 3 wherein upon pumpstoppage, flow of said small stream of bypassing liquid fuel is stoppedin response to decline of backpressure of the pump outlet stream,thereby preventing pump-pressurized liquid which was in the outletstream from draining into the carburetor after the pump has stopped.